4,144 research outputs found
Interplay of experimental harvesting and climate-related disturbance on benthic assemblages of rocky seashores
No full textAssessing responses of assemblages to compounded perturbations is a crucial goal of research on ecological impacts of current and predicted environmental changes. We examined the interactive effects of changes in temporal variance of 'storm-like' mechanical disturbance and in harvesting intensity of mussels (Mytilus galloprovincialis) on sessile assemblages associated with mussel beds on rocky shores in north Portugal. Response variables were measures of temporal variance in the abundance of individual taxa and in the structure of assemblages. Events of disturbance regularly distributed over the period of the experiment determined a lower temporal heterogeneity in assemblage structure than events characterized by larger temporal variance, but only in the presence of an intact mussel bed. The opposite pattern was documented in plots where mussels were completely removed. Univariate results indicated taxon-specific responses, with macroalgae, such as Corallina spp. and Porphyra linearis, showing patterns analogous to the multivariate one and grazing invertebrates displaying an opposite trend. This is one of the first manipulative examples aimed at examining effects of temporal variability of climate-related disturbance on systems increasingly depleted by concomitant stressors. The main finding was that effects of temporal variability of climate-related events of mechanical disturbance are mediated by the presence of intact stands of a foundation species. This may contribute to understanding and predicting responses of populations and assemblages under scenarios of concomitant climatic and non climatic changes
Type and timing of disturbance modify trajectories of recovery of rockpool assemblages at Aguda (NW Portugal)
No full textPatterns of recovery of rock pool assemblages were experimentally investigated along the rocky shore of Praia da Aguda (NW Portugal). The temporal variance in the structure of whole assemblages and abundance of individual algal and invertebrate organisms was examined after two experimental disturbances differing in intensity, i.e. one able to eliminate all the biota from the substratum, the other able to create a mosaic of bare patches interspersed within the remaining organisms. Two experimental trials were carried out (starting in March 2007 and July 2007, respectively), with a duration of the study of 13 months each. Multivariate results indicated a temporally consistent positive relationship between the intensity of disturbance applied and the temporal variance of the structure of assemblages. A similar response was documented at the univariate level by the encrusting coralline alga Lithophyllum incrustans and the foliose green algae of the genus Ulva, while both experimental disturbances decreased temporal fluctuations of the abundance of mussels. Mytilus galloprovincialis, compared to unmanipulated control. The present study has implications for understanding and predicting responses of intertidal assemblages to natural disturbances whose intensity is predicted to increase in the future, including climate events
Patterns of recovery of intertidal organisms after compounded anthropogenic disturbances
No full textCoastal habitats are exposed to increasing human and natural disturbances, including extraction of organisms and extreme climatic events. Patterns of recovery (i.e. convergence towards an unmanipulated control) of the structure of benthic assemblages, the total number, and the abundance of individual taxa were examined over a period of 15 mo after the end of a previous experiment. In that experiment, crossed manipulations of levels of mussel harvesting and of the temporal patterns of storm-related mechanical disturbance (in terms of changes in variance but not in the overall intensity) were performed on north Portugal rocky shores. Effects of past disturbances were mostly detected at 3 and 9 mo after the end of disturbances, while no significant differences between unmanipulated and treated assemblages were present after 15 mo. These findings confirm that intertidal assemblages subjected to even extreme combinations of past disturbances can recover in a relatively short time. Important effects present after 3 to 9 mo were associated with the timing of disturbance, likely depending on interactions with life-history traits such as peaks in reproduction and recruitment. Contrary to theories considering disturbances as opportunities for some organisms to replace competitors that dominate space in undisturbed conditions, we observed changes in the abundances of the same taxa rather than their replacement. The present evidence contributes to the understanding of how multiple anthropogenic pressures affect the ability of intertidal assemblages to recover after disturbance
Urban vs. extra-urban environments: scales of variation of benthic assemblages in north Portugal
No full textLittoral areas are subject to severe and increasing pressures resulting from human activities occurring along or next to the coast. In this study, patterns of variability in the structure of rocky intertidal benthic assemblages and in the abundance of individual taxa were compared between locations close to the coastal cities of Porto and Vila Nova de Gala (north Portugal) and reference locations far from it in much less urbanized conditions over a temporal scale of fourteen months and multiple spatial scales. Present findings indicated that assemblages were more heterogeneously distributed in the urban than in the extra-urban condition. The total number of taxa and several individual taxa displayed, in general, this same pattern of variability. This could be interpreted as the beginning of a habitat deterioration process with largely unpredictable consequences. The adopted sampling design supports the need for simultaneously including a range of temporal and spatial scales when evaluating responses of coastal marine biodiversity to anthropogenic disturbances
Draft toxicological profile for JP-5, JP-8, and jet A fuels
No full textA Toxicological Profile for JP-5 and JP-8 was released in 1998. This present edition supersedes any previously released draft or final profile.Chemical manager(s)/author(s): John Risher, Obaid Faroon, ATSDR, Division of Toxicology and Human Health Sciences, Atlanta, GA; Fernando Llados, Lisa Ingerman, Mario Citra, SRC, Inc., North Syracuse, NY
Reprogramming practice: revising design thinking through digital fabrication
No full textQuestioning the importance and impact of design thinking methodologies in the architectural design studios is a backbone of architectural education in twenty first century 3D printing and digital manufacturing are disruptive technologies that are changing architects and designers daily lives. These trends require new skills, based on a deep understanding of digital continuum from design to production, from generation to fabrication. This continuity transcends the merely instrumental contributions of a person-machine relationship to praxis, has begun to evolve as a medium that supports a continuous logic of design thinking and making. Design thinking methodologies associated with digital fabrication emerged as a leading technological and design issue of digital research and design. As designers, we are witnessing a no frontier between computational design and digital fabrication. For this paper is taken into consideration the work of two architecture studios that share a unique background on new methodologies by embracing the digital technology in their own practice. Their work reflects on new design methodologies facing the expansion of digital technology in architectural practice. This paper discusses the possibility of new design thinking methods driven by digital fabrication.info:eu-repo/semantics/publishedVersio
Reprogramming practice: revising design thinking through digital fabrication
No full textQuestioning the importance and impact of design thinking methodologies in the architectural design studios is a backbone of architectural education in twenty first century 3D printing and digital manufacturing are disruptive technologies that are changing architects and designers daily lives. These trends require new skills, based on a deep understanding of digital continuum from design to production, from generation to fabrication. This continuity transcends the merely instrumental contributions of a person-machine relationship to praxis, has begun to evolve as a medium that supports a continuous logic of design thinking and making. Design thinking methodologies associated with digital fabrication emerged as a leading technological and design issue of digital research and design. As designers, we are witnessing a no frontier between computational design and digital fabrication. For this paper is taken into consideration the work of two architecture studios that share a unique background on new methodologies by embracing the digital technology in their own practice. Their work reflects on new design methodologies facing the expansion of digital technology in architectural practice. This paper discusses the possibility of new design thinking methods driven by digital fabrication.info:eu-repo/semantics/publishedVersio
Shock tube study of JP-10 ignition delay time
No full textJP-10 (exo-tetrahydrodicyclopentadiene, C10H16) ignition delay times were measured in a preheated shock tube. The vapor pressures of the JP-10 were measured directly by using a high-precision vacuum gauge, to remedy the difficulty in determining the gaseous concentrations of heavy hydrocarbon fuel arising from the adsorption on the wall in shock tube experiments. The whole variation of pressure and emission of the OH or CH radicals were observed in the ignition process by a pressure transducer and a photomultiplier with a monochromator. The emission of the OH or CH radicals was used to identify the time to ignition. Experiments were performed over the pressure range of 151-556 kPa, temperature range of 1000-2100 K, fuel concentrations of 0.1%-0.55% mole fraction, and stoichiometric ratios of 0.25, 0.5, 1.0 and 2.0. The experimental results show that for the lower and higher temperature ranges, there are different dependency relationships of the ignition time on the temperature and the concentrations of JP-10 and oxygen
Dynamics of Network Formation Processes in the Co-Author Model
No full textThis article studies the dynamics in the formation processes of a mutual consent network in game theory setting: the Co-Author Model. In this article, a limited observation is applied and analytical results are derived. Then, 2 parameters are varied: the number of individuals in the network and the initial probability of the links in the network in its initial state. A simulation result shows a finding that is consistent with an analytical result for a state of equilibrium while it also shows different possible equilibria.Dynamics, Network, Game Theory, Model,Simulation, Equilibrium, Complexity
Close Future: Co-Design Assistant - How Proactive design paradigm can help
No full textThe present paper is focused on exploring a new paradigm in architectural design process that should raise the bar for a mutual collaboration between humans and digital assistants, able to face challenging problems of XXI century. Such a collaboration will aid design process freeing designer from middle level reasoning tasks, so they could focus on exploring - on the fly - design alternatives at a higher abstraction layer of knowledge. Such an assistant should explore and instantiate as much as possible knowledge structures and their inferences thanks to an extensive use of defaults, demons and agents, combined with its power and ubiquity so that they will be able to mimic behaviour of architectural design human experts. It aims other than to deal with data (1st layer) and simple reasoning tools (2nd layer) to automate design exploring consequences and side effects of design decisions and comparing goals (3rd layer). This assistant will speed up the evaluation of fresh design solutions, will suggest solutions by means of generative systems and will be able of a digital creativity
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